Mercury Archives

July 26, 2009February 10, 2017 by Abby Cessna

What are the Sizes of the Planets?

It is often difficult to grasp just how large the planets actually are. There are a number of ways to measure a planet, including diameter, volume, and surface area.

Mercury is the smallest planet in our Solar System since Pluto was demoted to a dwarf planet. It has a diameter of 4,879 km, and a surface area of 17.48 x 10⁷ km², which is only about 11% of Earth’s surface area. Mercury’s volume is even smaller in comparison at 6.083 x 10¹⁰km³, which is only 5.4% the volume of Earth.

Venus is similar in size to Earth, which earned it the title of Earth’s twin. Venus has a diameter of 12,100 km and a surface area of 4.6 x 10⁸ km². These measurements are 95% and 90% of Earth’s diameter and surface area respectively. With a volume of 9.38 x 10¹¹ km³, Venus’ volume is 86% of Earth’s.

Earth has a diameter of 12,742 km and a surface area of 5.1 x 10⁸ km². Its volume of 1.08 x 10¹²km³ gives the planet the largest volume of any of the terrestrial planets.

Mars is also a small planet, the second smallest in our Solar System. Mars’ diameter is 6,792 km, only about 53% of Earth’s diameter. At only 28% of Earth’s surface area, Mars has a very small surface area of 1.45 x 10⁸km². Mars’ volume of 1.63 x 10¹¹ km³ is only 15% of Earth’s volume.

All of the gas giants are larger in size than the four inner planets. Jupiter is the largest planet in our Solar System. It has a diameter of 143,000 km, which is more than 11 times the size of Earth’s diameter. The numbers only get larger from there. Jupiter has a surface area of 6.22 x 10¹⁰ km². That is 122 times greater than Earth’s surface area. Jupiter’s volume of 1.43 x 10¹⁵ km³ is an incredible number. You can fit 1321 Earths inside Jupiter.

Saturn is the second largest planet in our Solar System. It has a diameter of 120,536 km across the equator, and a surface area of 4.27 x 10¹⁰ km². With a volume of 8.27 x 10¹⁴ km³, Saturn can hold 764 Earths inside.

Uranus has a diameter of 51,118 km and a surface area of 8.1 x 10⁹ km². Although Uranus is much smaller than Jupiter, it is still large. With a volume of 6.83 x 10¹³ km³, you could fit 63 Earths inside the gas giant.

Neptune is slightly smaller than Uranus, but still very large. The planet has a diameter of 49,500 km. You could fit 57.7 Earths inside Neptune, which has a volume of 6.25 x10¹³ km³. Neptune has a surface area of 7.64 x 10⁹ km², which is 15 times Earth’s surface area.

We have written many interesting articles about the Solar Planets here at Universe Today. Here’s tWhat are the Different Masses of the Planets?, What Is The Atmosphere Like On Other Planets?, What is the Average Surface Temperatures of the Planets? and What are the Diameters of the Planets?

For more information, check out this website to learn all about the planets and this page from NASA to learn about the planets.

Astronomy Cast has an episode on each of the planets including Mercury.

July 22, 2009December 24, 2015 by Abby Cessna

Weight on Other Planets

Planets and other objects in our Solar System. Credit: NASA.

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Many children, and even adults, dream of visiting other planets and wonder what it would be like to stand on another planet. For one thing, your weight would be different on another planet, depending on a number of factors including the mass of the planet and how far you are away from the center of the planet.

Before we start, it’s important to understand that the kilogram is actually a measurement of your mass. And your mass doesn’t change when you go anywhere in the Universe and experience different amounts of gravity. Your weight is best measured in newtons. But since your bathroom doesn’t measure your weight in newtons, we’ll use kilograms. This is what your bathroom scale would say if you stepped on another world.

Mercury is the smallest planet in our Solar System, but it is dense. Because Mercury is so small, it has very little gravity. If you weighed 68 kg on Earth, you would only weigh 25.7 kg on Mercury.

Venus is very close to Earth in size and mass. Venus’ mass is roughly 90% of the mass of the Earth. Thus, it is no surprise that someone would weigh a similar amount on Venus. Someone who weighed 68 kg on Earth would weigh 61.6 kg on Venus.

Mars is quite a bit smaller than Earth with only 11% of our planet’s mass. Mars is larger than Mercury, but it is not as dense as the smaller planet. If you weighed 68 kg on Earth then you would weigh 25.6 kg on Mars. Since Pluto was demoted to a dwarf planet, Mars became the planet where you would weigh the least.

Jupiter is the largest planet in our Solar System with the most mass. Because of Jupiter’s mass, you would weigh more on that planet than on any other one in our Solar System. If you weighed 68 kg on Earth then you would weigh 160.7 kg on Jupiter, over twice your normal weight. That is if you could actually stand on Jupiter’s surface, which is impossible because it is a gas giant, and gas giants do not have solid surfaces.

Saturn is a gas giant best known for its planetary rings system. It is also the second biggest planet in our Solar System. Despite its mass though, the planet has a very low density and a lower gravity than Earth. If you weighed 68 kg on Earth, you would weigh 72.3 kg on Saturn.

Uranus is a gas giant without a solid surface. Although Uranus is larger in size than Neptune, it has less mass and therefore less gravity. You would only weigh 60.4 kg on Uranus, if you weighed 68 kg on Earth.

Neptune, the last planet in our Solar System, is a gas giant. If you weighed 68 kg on Earth, then you would weigh 76.5 kg on Neptune if you could stand on the planet’s surface.

Although the Moon is not a planet, it is one of the few objects that astronauts have actually visited. Because the Moon is so small, it has a low density and low gravity. If you weighed 68 kg on Earth, then you would only weigh 11.2 kg on the Moon.

Universe Today has a number of articles to check out including weight on the moon and mass of the planets.

If you are looking for more information then determine your weight on other planets and facts about the planets.

Astronomy Cast has an episode on gravity.

July 21, 2009December 24, 2015 by Fraser Cain

Exploration of Mercury

The MESSENGER spacecraft at Mercury (NASA)

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As one of the planets visible with the unaided eye, Mercury has been known before recorded history. But until the development of the telescope, the exploration of the Mercury was only unaided eye observations. Early cultures like the Mayans and ancient Greeks were diligent astronomers, and calculated the motions and positions of Mercury with tremendous accuracy.

But the exploration of Mercury really began with the invention of the telescope. Galileo Galilei was the first to turn his telescope on the 1st planet, seeing nothing more than a small disk. Galileo’s telescope wasn’t powerful enough to see that Mercury has phases, like the Moon and Venus. In 1631, Pierre Gassendi made the first observations of Mercury’s transit across the surface of the Sun, and further observations by Giovanni Zupi revealed its phases. This helped astronomers to conclude the Mercury orbited the Sun, and not the Earth.

Because Mercury is so small, and located so close to the Sun, astronomers weren’t able image features on its surface with any accuracy. It wasn’t until the 1960s, when Soviet scientists bounced radio signals off the surface of Mercury that astronomers got any sense of what its surface was like. These radio reflections also helped astronomers discover that Mercury’s day length is 59 days; almost as long as its year of 88 days.

But the best Mercury exploration happened when NASA’s Mariner 10 spacecraft first flew past Mercury in 1974. It revealed that Mercury’s surface is pockmarked with craters like the Earth’s moon. And like the Moon it has flat regions filled in with lava flows. After two additional flybys Mariner 10 ended up mapping only 45% of Mercury’s surface.

The next mission to explore Mercury was NASA’s MESSENGER spacecraft, launched on August 3, 2004. It made its first Mercury flyby on January 14, 2008, mapping more of Mercury’s surface. MESSENGER will eventually go into orbit around Mercury, mapping its surface in great detail and answering many unknown questions about Mercury and its history.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.

Want more information on Mercury? Here’s a link to NASA’s MESSENGER Misson Page, and here’s NASA’s Solar System Exploration Guide to Mercury.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

References:
NASA Solar System Exploration: Missions to Mercury
NASA: Planetary Science

July 9, 2009December 24, 2015 by Fraser Cain

Have Humans Visited Mercury?

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Have astronauts from Earth ever stepped foot on Mercury? No, Mercury has been visited by spacecraft from Earth, but no human has ever gone into orbit around Mercury, let alone stepped on the surface. Just what would it take to visit Mercury?

Humans attempting to visit Mercury would find a similar environment to the Moon. Mercury is airless, so they would need a spacesuit to protect themselves from the vacuum of space. However, the temperatures on Mercury are much greater. During the daytime, the surface of Mercury at the equator rises to 700 Kelvin (427 degrees C). Just for comparison, the surface of the Moon only rises to 390 Kelvin (117 degrees C) during the daytime. So you would need some kind of protection from the intense heat.

But then, nighttime on Mercury dips down to only 100 Kelvin (-173 degrees C) – that’s the same low temperatures you get on the Moon at night. So an astronaut’s spacesuit would need to be able to keep an astronaut warm when they’re in the shade.

The travel time to the Moon is only about 3 days. But the travel time to Mercury is much longer. That’s partly because Mercury is much further away – 10s of millions km. But spacecraft also need to take special trajectories so they can get into orbit around Mercury. All of the spacecraft that have visited Mercury have taken longer than a year to reach the planet. That would be a long, hot journey for astronauts.

Maybe some day in the future humans will visit Mercury, but it hasn’t happened yet.

Want more information on Mercury? Here’s a link to NASA’s MESSENGER Misson Page, and here’s NASA’s Solar System Exploration Guide to Mercury.

We have also recorded a whole episode of Astronomy Cast that’s just about planet Mercury. Listen to it here, Episode 49: Mercury.

Reference:
NASA Star Child: Mercury

July 7, 2009December 24, 2015 by Abby Cessna

Discovery of the Planets

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We actually only know the exact date of when a few of the planets were discovered. Five of the planets, not including Earth, have been known to exist for thousands of years – Mercury, Mars, Venus, Jupiter, and Saturn. The Ancient Greeks and Romans wrote about the planets many centuries ago. Because the planets look like stars to the naked eye, that is where the term planets comes from. Because the planets move in the sky, they were termed wandering stars. The term planet comes from the Greek word for wanderer, “planetes.” Many ancient people thought that the planets were gods, so they gave them the names of their gods. All of the planets, except Earth have names of Roman deities.

The other three planets – Uranus, Neptune, and Pluto – were not discovered until at least the 1700’s. Pluto is no longer a planet since it was reclassified as a dwarf planet in 2006. It was known as the ninth planet for 70 years though, so its discovery will be included here. Uranus was discovered in 1781 by the famous astronomer Sir William Herschel, although that was not the first sighting of it. The planet had been sighted as early as 1690 by the English astronomer John Flamsteed. It was also sighted by Pierre Lemonier in the mid 1700’s. Sir Herschel at first thought that Uranus was a comet, but he noticed the irregularities early on and compared it to a planet in his notes.

Because Neptune cannot be seen without the help of a telescope, it was not discovered until after 1610, when Galileo created the telescope. Alexis Bouvard, a mathematician, saw that another planet had to be affecting Uranus’ orbit, so astronomers started looking for it. Two astronomers, John Couch Adams and Urbain Le Verrier, discovered Neptune independently or rather made the calculations and determined where Neptune could be found. The planet turned out to be 1° from Verrier’s calculations and 12° from Adams’. There was a dispute between France and England over who discovered the new planet because Adams and Verrier are from England and France respectively.

Pluto was the last planet discovered, although that distinction returned to Neptune when Pluto was reclassified as a dwarf planet. Pluto was discovered in 1930 by the astronomer Clyde Tombaugh. Many people had been searching for a ninth planet – the elusive planet X – for quite a while. Since Pluto was discovered near the calculated location of planet X, they thought the two planets were one and the same. Later, astronomers realized that there was no such planet X.

Universe Today has a number of articles on the planets including who discovered Neptune and the planets of our Solar System.

Check out these other articles including mathematical discovery of the planets and the planets.

Astronomy Cast has episodes on all of the planets including Mercury.

July 7, 2009December 24, 2015 by Abby Cessna

Names of the Planets

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You may recognize the names of the planets from your high school literature course or a history class. That is because many of the planets were first discovered by ancient civilizations, and so planets are named after their gods.

The Romans named Mercury after the messenger of the gods because it appears to move so quickly.

Venus was named after the Roman goddess of love because of its shining presence. The planet is the brightest object in the sky beside the Moon and the Sun. A number of other cultures also named Venus after their own gods or goddesses of love and war.

Earth is the only planet not named after a god. The name is based on Germanic and Old English words for “ground.”

Mars was named after the Roman god of war because of its red color, which reminded people of blood. Other civilizations also had names for the planet based on its color. The Egyptians called it “Her Desher,” which means “the red one.”

Jupiter was named after the king of the gods – Zeus by the Greeks and Jupiter by the Romans. Ancient civilizations most likely named this planet after the most powerful god because of its size. Jupiter is the largest and most massive planet in our Solar System.

Saturn was named after the father of the king of gods as well as being the god of agriculture and harvest. In mythology, Saturn had taken the position of king of the gods from his own father, Uranus, and then Jupiter overthrew him. Saturn is the last planet that can be seen from Earth without the aid of a telescope.

Uranus was not discovered until 1781 by Sir William Herschel, so it was not necessarily going to be named after a Roman god. In fact, Herschel named the planet “Georgium Sidus” in honor of George III who was King of England at the time. Others called the planet Herschel in honor of the astronomer who had discovered it. The name Uranus, which is the name of the Roman god who is the father of Jupiter, was suggested by the astronomer Johann Bode. That name was widely accepted in the mid 1800’s, and it fit in with the other planets, which all had names from mythology.

Neptune had been observed by a number of astronomers, but they believed it was a star. Two people, John Couch Adams and Urban Le Verrier, calculated the planet’s location. Johann Galle, the astronomer who discovered the planet using Verrier’s calculations, wanted to name the planet after Verrier. Many astronomers objected though, so it was named after Neptune the Roman god of the sea. The name was very fitting because the planet is a bright sea blue.

Universe Today has a number of articles on the planets including facts about the planets and the planets of the solar system.

If you are looking for more information on the planets take a look at the planets and interesting facts about the planets.

Astronomy Cast has episodes on all of the planets, so start with Mercury.

January 23, 2008December 26, 2015 by Nancy Atkinson

Mercury in Living Color

The MESSENGER science team released more pictures from the Jan. 14 flyby, including what we’ve all been waiting for, the first one in color! But if you’re looking for spectacular, eye-catching color, well, sorry, its just not part of Mercury’s make-up.

The color image was created by combining three separate images taken through MESSENGER’s Wide Angle Camera (WAC) filters in the infrared, far red, and violet wavelengths (red, green, and blue filters for this image.) MESSENGER’s eyes can see far beyond the color range of the human eye, and the colors seen in this image are somewhat different from what a human would see.

Creating a false-color image in this way brings out color differences on Mercury’s surface that cannot be seen in the black and white images released earlier.

The WAC has 11 narrow-band color filters, in contrast to the two visible-light filters and one ultraviolet filter that were on Mariner 10’s camera. By combining images taken through different filters in the visible and infrared, the MESSENGER data allow Mercury to be seen in a variety of high-resolution color views not previously possible. This visible-infrared image shows an incoming view of Mercury, about 80 minutes before MESSENGER’s closest pass of the planet from a distance of about 27,000 kilometers (17,000 miles).

I love this image of Mercury’s south pole limb. It shows the terminator; the transition from the sunlit, day side of Mercury to the dark, night side of the planet. In the region near the terminator, the sun shines on the surface at a low angle, causing the rims of craters to cast long shadows, which brings out the height differences of the surface features. This image was acquired about 98 minutes after MESSENGER’s closest approach to Mercury, when the spacecraft was at a distance of about 33,000 kilometers (21,000 miles).

And here’s one for the scientist in you: the first data returned from MESSENGER’s Mercury Atmospheric and Surface Composition Spectrometer (MASCS). What the image on the right shows with the bar-graph type lines is a high-resolution spectra of the planet’s surface in ultraviolet, visible, and near-infrared light. The image on the left shows a portion of the ground-track along which the MASCS instrument took over 650 observations of the surface. The area is about 300 kilometers (190 miles) across. For those of you not fluent in spectra-ese, this shows the relative amount of sunlight reflected from the surface at wavelengths from the ultraviolet to the visible (rainbow) to the infrared.

Original News Source: MESSENGER Press Releases

January 17, 2008December 26, 2015 by Nancy Atkinson

A View of Mercury’s Far Side

Images and data are arriving from MESSENGER’s recent flyby of Mercury. Scientists from NASA and the Johns Hopkins Applied Physics Lab are pouring over high resolution images of the side of the planet that has never before been imaged by a spacecraft. From these images, planetary geologists can study the processes that have shaped Mercury’s surface over the past 4 billion years. Let’s take a look at some of the images snapped by MESSENGER on January 14:

This image was taken just 21 minutes after MESSENGER’s closest approach to Mercury, at a distance of only 5,000 kilometers (3600 miles). It shows a region about 170 km (100 miles) across. Visible are a variety of surface features, including craters as small as about 300 meters (about 300 yards) across. But the most striking part of the image is one of the highest and longest cliffs yet seen on Mercury. About 80 km (50 miles) long, it curves from the bottom center up across the right side of this image. Scientists say that great forces in Mercury’s crust must have thrust the terrain occupying the left two-thirds of the picture up and over the terrain to the right. An impact crater has subsequently destroyed a small part of the cliff near the top of the image.

This image shows a previously unseen crater with distinctive bright rays of ejected material from the impact extending outward, providing a look at minerals from beneath Mercury’s surface. A chain of craters nearby is also visible. Studying impact craters provides insight into the history and composition of Mercury. The width of the image is about 370 kilometers (about 230 miles), and was taken about 37 minutes after MESSENGER’s closest approach. This image is the 98th in a set of 99 images that were taken to create a large, high-resolution mosaic of this region of Mercury. Hopefully this anticipated mosaic will be released at a planned press conference on January 30.

As MESSENGER approached Mercury on January 14, 2008, about 56 minutes before the spacecraft’s closest encounter, the Narrow-Angle Camera captured this view of the planet’s rugged, cratered landscape illuminated by the Sun. Although this crater has been imaged before by Mariner 10, MESSENGER’s modern camera has revealed detail that was not well seen by Mariner including the broad ancient depression overlapped by the lower-left part of the Vivaldi crater. Its outer ring has a diameter of about 200 kilometers (about 125 miles). The image shows an area about 500 km 9300 miles) across and craters as small as 1 kilometer (0.6 mile) can be seen. It was taken from a distance of about 18,000 km (11,000 miles.)

The MESSENGER (Mercury Surface Space Environment Geochemistry and Ranging) Science Team has begun analyzing these high-resolution images to unravel the history of Mercury, as well as the history of our solar system.

Original News Source: MESSENGER Website

January 15, 2008December 26, 2015 by Nancy Atkinson

A Winged MESSENGER Flies By Mercury

On January 14 the MESSENGER spacecraft skimmed just 200 kilometers (124 miles) above the surface of Mercury in the first of three flybys of the planet. Today (Jan. 15) the spacecraft will turn back towards the Earth to start down-linking the on-board stored science data it acquired during the flyby. The probe’s equipment gathered data on the mineral and chemical composition of Mercury’s surface, its magnetic field, its surface topography and its interactions with the solar wind. “This was fantastic,” said Michael Paul, a mission engineer. “We were closer to the surface of Mercury than the International Space Station is to the Earth.”

The closest approach was on the planet’s night side, the side facing away from the sun, and the spacecraft flew in the region along the equator. The scientific results will be available for the public at the end of January.

“The engineers and operators pulled off a tremendous feat, acquiring and locking onto the downlink signal from the spacecraft within seconds, providing the necessary Doppler measurements for the Radio Science team.” said MESSENGER Mission Systems Engineer Eric Finnegan, of the Applied Physics Lab in Laurel, Maryland. “The spacecraft is continuing to collect imagery and other scientific measurements from the planet as we now depart Mercury from the illuminated side, documenting for the first time the previously unseen surface of the planet.”

The signal from the spacecraft is tracked by the Deep Space Network, an international network of antennas that supports space missions.

In addition to Monday’s rendezvous, MESSENGER is scheduled to pass Mercury again this October and in September 2009, using the pull of the planet’s gravity to guide it into position to begin a planned yearlong orbit of the planet in March 2011. By the time the mission is completed, scientists also hope to get answers on why Mercury is so dense, as well as determine its geological history and the structure of its iron-rich core and other issues.

MESSENGER stands for Mercury Surface, Space Environment, Geochemistry and Ranging. Launched in 2004, it already has flown past Venus twice and Earth once on its way to Mercury.

Only one spacecraft has previously visited Mercury. Mariner 10 flew past the planet three times in 1974 and 1975, and mapped about 45 percent of its surface.

With Pluto now considered a dwarf planet, Mercury is the solar system’s smallest planet, with a diameter of 3,032 miles, about a third that of Earth.

A surface feature of great interest to scientists is the Caloris basin, an impact crater about 800 miles in diameter, one of the biggest such craters in our solar system. It likely was caused when an asteroid hit Mercury long ago. Scientists hope to learn about the subsurface of the planet from studying this crater.

True to its name, temperatures on the closest plant to the sun are quite “mercurial,” as Mercury experiences the largest swing in surface temperatures in our solar system. When its surface faces the sun, temperatures hit about 800 degrees Fahrenheit (425 Celsius), but when its faces away from the sun they can plummet to minus-300 Fahrenheit (minus-185 Celsius).

Original News Source: Reuters